As the term suggests, agroforestry combines agriculture and forestry. This definition oversimplifies the wide range of practices that fall within the scope of agroforestry, however. Agroforestry can also involve the disciplines of horticulture, range management, urban or regional planning and wildlife management.
Because of the wide range of benefits provided by adding trees and shrubs to the landscape, agroforestry practices may be used by farmers, ranchers, city planners, park and recreation managers, landscapers and engineers.
Agroforestry uses trees and shrubs to add value to the landscape, whether that landscape is a field of grain crops, a vegetable garden, a highway right-of-way or an urban area. Producers benefit through reduced costs, higher incomes, improved wildlife habitat and increased land values.
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| In this alley cropping system, a field crop is grown between widely spaced rows of black walnut trees. Photo: Nebraska Forest Service. |
Trees and shrubs provide commercially valuable products. From trees we get lumber, paper and firewood. Both trees and shrubs produce fruits, nuts and woody floral products. These are only a few of the products agroforestry can provide, and these products have many uses.
Agroforestry seeks to combine the economic value gained from these tangible products with values that are harder to quantify, such as improved water quality, environmental health and natural beauty.
Interactions
Trees and shrubs can have a profound effect on both the biotic (living) and abiotic (non-living) factors within their surrounding environment.
Tree leaves and branches intercept solar radiation. They provide shade, which reduces water loss through evaporation from the soil and transpiration from plants. Shade also moderates the soil temperature in both extreme heat and cold. When leaves, needles and twigs fall from trees, they add organic matter to the soil.
Trees also buffer the wind. This reduces wind erosion, blowing dust and snow and pesticide drift. Networks of tree roots also hold soil in place, reducing water erosion.
Both trees and shrubs provide nesting and food for birds. This is desirable because birds may help control insect pests in nearby crops.
Benefits of Interaction
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| This riparian buffer helps protect the stream from runoff that may contain sediments and other pollutants. Photo: Nebraska Forest Service. |
Agroforestry practices have multiple impacts in a land-use system:
- protect topsoil, crops, animals and people;
- increase productivity of crops;
- reduce chemical, physical and biological energy inputs;
- increase water-use efficiency of plants and animals;
- improve water quality;
- diversify local and regional economies; and
- enhance biodiversity and landscape heterogeneity.
There is also the risk of negative interactions between plants and trees in agroforestry systems. For example, trees could completely shade out nearby forage or field crops or compete with surrounding plants for water and nutrients.
Because of these possible negative interactions, agroforestry requires a knowledge of trees' and shrubs' characteristics and their possible interactions with crops, wildlife, livestock, soil, water and air.
The central goal of agroforestry is to optimize the benefits obtained through the interaction of trees with their plant and/or animal surroundings while minimizing the possible negative effects of the interactions. This requires careful planning.
There are five practices used to incorporate trees into the landscape:
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When designed correctly, windbreaks can be effective in reducing heating and cooling costs. Photo: Nebraska Forest Service. |
- Windbreaks are linear plantings of trees and shrubs in agricultural fields, around buildings or along roads. They protect crops, buildings, people, livestock and roadways from harsh winds and blowing snow and reduce noise and odor from livestock operations.
- Silvopasture includes trees integrated into an existing grassland or grassland established under a thinning forest. Silvopasture provides shelter and shade for animals, beautifies the landscape and produces two or more crops (trees, livestock and hay) on the same land.
- Alley Cropping involves linear plantings of trees and shrubs in agricultural fields. The plantings in alley cropping are planted closer together than the linear plantings of windbreaks. Alley cropping mixes trees and crops on a smaller scale to provide a sheltered environment for high-value food and forage crops.
- Riparian Buffers consist of trees and shrubs established adjacent to bodies of water. Riparian buffers trap sediment, reduce streambank erosion, create wildlife habitat and improve water quality.
- Forest Farming is the practice of producing commercially valuable products in the shade of trees.
A Brief History of Agroforestry
Agroforestry is a very old practice that likely grew out of necessity as primitive farmers carved crop land out of forested areas. In these earlier times, the availability of wild foodstuffs, as well as wood for fuel and construction, was very important to the survival of individuals, families and entire cultures. The principles of agroforestry have been in use for centuries, most commonly in tropical and subtropical regions.
In early America , forests presented an obstacle to settlers' safety, traditional European farming techniques and westward expansion. Due to this, much native forest cover was lost to settlement from the 1600s to 1800s. In fact, the existing tracts of forest in eastern North America represent only a fraction of the original forested areas. However, as settlers moved to the Midwest and Great Plains , many brought with them seeds of familiar landscape plants and fruit and nut trees to plant on their new homesteads. This was the beginning of agroforestry as we know it.
In 1914, Russell Smith, an economic geographer at Columbia University in New York City , advocated the use of permanent tree-protected areas to maximize production on arable land. His ideas were opposed until the Great Depression and ‘Dust Bowl' fueled interest and research in this area.
The post-World War II economic and industrial boom lessened interest in agroforestry. However, new agricultural technologies and innovative approaches to agroforestry were developed in the 1960s and 1970s. This, coupled with increased interest in conservation and concern for dwindling natural resources, once again brought attention to agroforestry.
Today, agroforestry research is conducted by universities, government agencies, individual agricultural producers and other organizations. Agroforestry is practiced by private citizens and public institutions alike.
Get information on government programs that provide assistance to landowners who implement agroforestry practices into their landscape.
